Method for adjusting a side of a strip of flexible material to a reference side and apparatus for feeding a belt strip on a rotating building drum

Abstract: Method for adjusting the shape of at least one side (36) of a strip (13) of flexible material to the shape of a reference side (36') concerned. The method comprises the steps of determining the shape of the at least one side (36) of the strip (13), comparing the shape as determined of the at least one side with the shape of the reference side (36'), and adjusting the shape as determined of the at least one side to the shape of the reference side, depending on the outcome of the comparison. Belt strip feeding apparatus for feeding a belt strip (17) on a rotating building drum (1). The feeding apparatus is provided with a supply reel (2) for containing belt material (13), with means for unwinding belt material from the supply reel, with conveying means (6),(7),(8) for conveying the unwound belt material to the building drum, with cutting (9) means placed above the roller conveyor (6) for cutting the belt material into a belt strip (17). The feeding apparatus comprises means (24) for adjusting at least one side of the belt strip to a reference side concerned, according to the method.

Description: The invention relates to a method for feeding a belt strip to a rotating building drum. The invention further relates to a belt strip feeding apparatus for feeding a belt strip to a rotating building drum. The method and apparatus according to the invention can especially be applied in the manufacture of pneumatic tyres, nowadays mainly radial tyres, for vehicles. In the manufacture of these tyres, strips of flexible material are mounted onto a building drum to build a belt for the pneumatic tyre on the building drum. In general, such a strip will be elongated and have two long and two short circumferential sides. A method for feeding a belt strip to a rotating building drum is known from e.g. US-A-4 608 890, said method comprising the steps of: a) unwinding belt material having opposite longitudinal sides from a supply reel, b) conveying the belt material in a direction of conveyance at a velocity of conveyance from the supply reel to a fixing element by conveying means, said longitudinal sides of the belt material being substantially parallel to the direction of conveyance, said conveying means comprising a first conveyor, c) cutting the belt material into a belt strip by cutting means placed above the conveying means, said belt strip being elongated and having two long circumferential sides and two short circumferential sides, said belt strip comprising: a central rectangular part having two long sides and an imaginary centre line, the direction of conveyance of the first conveyor being parallel to the imaginary centre line, a triangular leading end, situated downstream, the one short, leading circumferential side of the strip being formed by the hypotenuse of the leading end and a short side of the leading end lying in the extension of one of the long sides of the central part, the hypotenuse and the short side of the leading end enclose an acute angle and the one long side of the central part and the short side of the leading end forming the one long circumferential side of the strip, a triangular trailing end, situated upstream, the other short, trailing circumferential side of the strip being formed by the hypotenuse of the trailing end and a short side of the trailing end lying in the extension of the other side of the central part, the hypotenuse and the short side of the trailing end enclosing an acute angle and the other long side of the central part and the short side of the trailing end forming the other long circumferential side of the strip. A belt strip feeding apparatus for feeding a belt strip to a rotating building drum is further known from US-A-4 608 890, which feeding apparatus comprises: a supply reel for containing belt material, means for unwinding belt material from the supply reel, conveying means for conveying the unwound belt material to the building drum, cutting means placed for cutting the belt material into a belt strip, such that the belt strip is elongated and has two long circumferential sides and two short circumferential sides and that the strip comprises: a central rectangular part having two long sides and an imaginary centre line, the direction of conveyance of the roller conveyor being parallel to the imaginary centre line, a triangular leading end, situated downstream, the one short, leading circumferential side of the strip being formed by the hypotenuse of the leading end and a short side of the leading end lying in the extension of one of the long sides of the central part, the hypotenuse and the short side of the leading end enclosing an acute angle and the one long side of the central part and the short side of the leading end forming the one long circumferential side of the strip, a triangular trailing end, situated upstream, the other short, trailing circumferential side of the strip being formed by the hypotenuse of the trailing end and a short side of the trailing end lying in the extension of the other side of the central part, the hypotenuse and the short side of the trailing end enclosing an acute angle and the other long side of the central part and the short side of the trailing end forming the other long circumferential side of the strip. In the method described in US-A-4 608 890, flexible material is cut into strips by means of a cutting mechanism, the front end and the rear end forming an angle with the imaginary centre line of the strip. As a consequence of the variation in angle under which the strip is cut, the angle of the front end and the rear end often differ. In this known method the path of the knife of the cutting mechanism is determined during cutting of the front end and the rear end. The path of the knife as determined during cutting of the rear end is compared with the path of the knife during cutting of the front end. A pivotable manifold is placed on the rear end, said pivotable manifold engaging the rear end. Depending on the difference in the measured paths of the knife, the pivotable manifold together with the rear end is pivoted over the measured angle of difference. Although the aim of this known method is to render the angles of the front and rear end similar, actual practice has shown that rendering the angle equal is not always carried out in a satisfactory manner. It is, among other things, an object of the present invention to provide a method and an apparatus for adjusting the shape of at least one side of a strip of flexible material to a reference side, in which this adjustment can be carried out satisfactorily in almost all cases. For this purpose, the present invention provides a method for feeding a belt strip to a rotating building drum, as described in claim 1. Particular embodiments of the invention are subject of the dependent claims 2 to 11. The invention is based on the insight that after cutting the front and the rear end of the strip according to the known method, the shape of the end concerned can change as a result of relaxation of tensions in the flexible material. Consequently, the shape of an end of the strip can differ considerably from the determined path of the knife. Furthermore in the known method, the rear and the front end are engaged in their entirety and pivoted by the pivotable manifold. In actual practice, it has been found that in certain types of strip material this can cause deformations in the strip material, which deformations harm the quality of the final product in which the strip is used. By determining in accordance the invention the shape of the side of the strip which is to be adjusted itself, the adjustment of this side to a reference side concerned can be carried out more accurately. In addition, deformations during adjustment are at least largely avoided according to the invention since the adjustment of the shape of the at least one side of the strip is carried out dynamically during conveyance of the strip over the transition from the first conveyor to the fixing element. By carrying out the adjustment dynamically, that is to say that sections of the at least one side are adjusted successively, instead of statically, i.e. adjusting the entire side all at once, not only the deformations occurring in the adjustment of a section are small, but these small deformations can also be assimilated better by the flexible material without an undesirable non-correctable deformation occurring in the strip. In actual practice, it has furthermore transpired that the dynamic adjustment of the at least one side of the strip can be carried out quickly and, for all strip materials, correctly, by executing a shifting of the strip relative to the fixing element transverse to the direction of conveyance during the transition. If the material harbours many tensions, it may happen that the pointed end of the strip looses its shape at the transition from the first conveyor to the fixing element. By determining, comparing with a reference side and adjusting the shape of the at least one side during the transition from the first conveyor to the fixing element, this loss of shape is at least partially avoided. The at least one side having an adjusted shape is fixed by means of a fixing element. This allows for many adjustments within a certain period of time, in which strips having one or more sides that have already been adjusted can be stored on the fixing element. The number of sections into which the at least one side should be divided in order to avoid undesirable deformation depends, among other things, on the material used and can be determined by a person skilled in the art through simple experiments. In EP-0 430 519 a method and apparatus for supplying a cut belt-shaped member onto a winding drum are described. In this known method only the difference in angle of the cut edges - the extending directions - of the cut edges are detected after cutting by two sensors. In order to be able to detect the difference in angle between these cut edges - these extending directions -, the belt-shaped member is stopped several times and is rearwardly displaced, as seen in the general direction of conveyance. Furthermore, EP 0 430 519 only teaches correcting the direction (or angle) of the cut edge of the belt-shaped member by rotating the table plus cut belt-shaped member to eliminate the difference in angle between the two cut edges, which results in a deformation of the material. The method according to the present invention differs from the teachings of EP 0 430 519 A3 , amongst other things, in the following points: a. the step of determining, comparing and adjusting according to the present invention takes place while the belt strip is being conveyed in the general direction of conveyance over the transition, b. the inventive adjustment is carried out dynamically, thus avoiding deformations in the strip material which result from rotating the complete length of the cut edge of the strip, c. the shape of the side is determined in the present invention, while only the extending direction of an edge is determined by EP 0 430 519 A3. From JP-A-02-165937 it seems to be known that deformation is corrected by means of pulling a belt strip into an abutting surface. Since the present invention does not use abutting surfaces to correct the shape of a side of a belt strip, this document seems not to be relevant. Furthermore JP-A-02-165937 does not describe that the shape of at least one side of the belt strip is determined. In EP 0 104 339 a means and method for applying innerliner material to a tyre building drum and more particularly a means and a method for cutting and applying the innerliner material is described comprising precise centering of the innerliner material. Said means comprises an air table providing an air-bearing, a fibre optic guidance unit to determine the lateral position of the innerliner material, a lateral adjustment unit comprised of a manifold for laterally positioning the innerliner material, a gripper unit for grasping the innerliner material and an applicator to apply the innerliner material to the building drum. In contrast to the present invention the means as described in EP 0 104 339 neither determine the shape of a side of the innerliner, nor do they compare or adjust this shape to the shape of a reference side. Furthermore, the innerliner according to EP 0 104339 is cut perpendicular to its centreline and has no triangular leading or trailing end. In US 4,465,531 a method of forming a closed loop of a flexible strip is described comprising conveying an elongated flexible strip in a predetermined longitudinal direction to a predetermined position on a predetermined conveyance plane, detecting the locations and geometry of end portions of the strip while the strip is being conveyed. The locations and the geometry of the end portions of the strip are detected in the field of vision of a television camera. In contrast to the present invention US 4,465,531 does not describe that the determination of the shape of a side of the strip takes place by determining the shape of sections of the side during conveyance of the strip over a transition and does not describe that the shape of the sections of the side are compared to the shape of the sections of a reference side. In EP 0 376 357 a centering device comprising means for continuously posing the centre of the distance between the two edges of all portions of a strip onto the desired diametral circumferential line of a drum. Said device comprises means for transmitting light rays to the strip and means for detecting the light rays reflected by the strip. In contrast to the present invention EP 0376 357 neither teaches the determination of the shape of a side of a strip, nor does it teach comparing nor adjusting this shape to the shape of a side of a reference strip. In US 4,769,104 an apparatus for sticking a tyre component member having cords inserted therein at a predetermined bias angle and having its opposite ends cut respectively in parallel to the cords into a fixed length onto a forming drum upon manufacturing a rubber tyre. This apparatus comprises a belt conveyor containing attracting means therein for receiving the cut tyre component member and conveying it to the forming drum, widthwise positioning means for correcting a position in the widthwise direction of the tyre component member from its both lateral sides, and front and rear end reshaping means adapted to butt against cut edge surfaces at the front end and the rear end of the tyre component member for correcting the shapes of these cut edges. In contrast to the present invention US 4,769,104 does not describe the determination of the shape of a side of a strip during conveyance over a transition and does use abutting surfaces to reshape cut edges. In order to be able to further convey the strip having the at least one adjusted side for further working, an embodiment of a method according to the invention is characterized in that the fixing element is formed by a conveyor. Especially when the strip has to be wound onto a building drum, which building drum can form the fixing element, or when the strip is conveyed via the second conveyor to the building drum, practice has shown that shifting can be carried out the easiest by shifting the first conveyor perpendicularly to its direction of conveyance. In the manufacture of these tyres, strips of flexible material are mounted onto a building drum to build a belt for the pneumatic tyre on the building drum. In order to obtain a good quality pneumatic tyre, the shape of the strip should not deviate too much from a reference shape and the strip should be placed in an accurate position on the building drum. Depending on the quality standards applied to the pneumatic tyre, the leading and the trailing short circumferential sides should fit together when placed on the building drum. The quality of the pneumatic tyre, into which belt strips having steel reinforcement cords have been built, is, for instance, checked after vulcanization by means of X-rays. The known method for adjusting the short circumferential sides provides, to an extent, an improvement in quality of the pneumatic tyre. However, depending on the quality standards set for the pneumatic tyre, the failure percentage remains relatively high. This is caused, among other things, by the above-mentioned deformations which are introduced into the material during the adjustment, but also because when one of the short circumferential sides is rotated, a corner thereof can end up outside the allowed range of tolerance at too big or too small a distance from the imaginary centre line of the strip. This corner, also called dog ear, has a negative influence on the failure percentage. Embodiments of the method according to the invention provide the possibility of drastically reducing this failure percentage. In these embodiments the at least one side is formed by the short side of the leading end or by the hypotenuse of the leading end. Depending on the quality of the belt material, and the accuracy of the cutting process with which the belt material is cut into belt strips, an adjustment of one of the sides of the leading end can suffice to ultimately obtain a sufficiently high quality of the pneumatic tyre. In order to obtain a uniformly rotating pneumatic tyre as final product, the weight of the strip must be evenly spread over the pneumatic tyre. This can be achieved by centering the central part of the strip around the imaginary centre line. This centering can be effected in a simple manner by an embodiment of the method according to the invention which further comprises the steps of determining the shape of the centre line of the central part, comparing the shape of the centre line of the central part with a shape of a reference centre line and adjusting the shape of the centre line of the central part to the shape of the reference centre line. In further preferred embodiments of a method according to the invention the at least one side is formed by the hypotenuse of the trailing end or by the short side of the trailing end. This renders it possible to adjust one of the sides of the trailing end to a reference side in a simple manner. When the second reference hypotenuse corresponds to the first reference hypotenuse, then the trailing short circumferential side and the leading short circumferential side can fit together on a building drum. Determining the shape of the at least one side is done in an economical yet accurate way by means of two linear CCD-cameras. According to another aspect the present invention provides a belt strip feeding apparatus for feeding a belt strip to a rotating building drum as described in claim 12. Further particular embodiments of the invention are subjed of the dependent claims 13 to 19. Further advantages of a method and belt strip feeding apparatus according to the invention will become clear from the description given hereafter, in which, by way of example, some embodiments of the invention will be described by means of the drawing. In the drawing: figure 1 shows a schematic side view of a belt strip feeding apparatus according to the invention; figures 2, 3 and 4 show a schematic top view of a part of the belt strip feeding apparatus according to figure 1; figure 5 shows a schematic side view of a conveyor belt to be used in a belt strip feeding apparatus according to the invention; figure 6 shows a schematic enlarged representation of a part of figure 3; figure 7 shows a schematic side view of figure 6; figure 8 shows a schematic view from the roller conveyor, showing the CCD-cameras; figure 9 schematically shows a reference belt strip; figure 10 schematically shows a possible shape of an actual belt strip; figure 11 shows a schematic top view of the transition between roller conveyor and conveyor belt, the corner of the belt strip being situated at the transition; figure 12 shows a schematic top view analogous to figure 11, the belt strip covering the transition; figure 13 schematically shows a determining grid for determining the shape of a side of the belt strip; figure 14 schematically shows the adjustment of the shot, trailing circumferential side to the short, leading circumferential side; and figure 15 shows another field of application of the invention. Before further going into the subject of actually adjusting the shape of at least one side of a strip of flexible material to a reference side, an apparatus will first be described in which the adjusting of the shape can be used. The belt strip feeding apparatus, represented schematically in figure 1, for feeding a belt strip to a rotating building drum 1 comprises two exchangeable supply reels 2 and 3 for containing belt material. The belt material is unwound by means 4 and 5 from the supply reels 2 and 3, respectively, and conveyed to the building drum 1 via conveying means 6, 7, 8 and 6', T and 8'. Each of the conveying means successively comprises a roller conveyor 6, 6', a conveyor belt 7, 7' and a mounting conveyor 8, 8' for mounting the belt strip onto the building drum. A cutting means 9, 9' is placed above every roller conveyor 6, 6' for cutting the belt material into a belt strip. The belt strips supplied by the conveying means 6, 7, 8 and 6', 7' and 8' are one by one wound around the building drum 1, such that a packet consisting of superimposed belt strips is built on the building drum 1. The belt apparatus comprises determining means 10 which are placed at the transition from the roller conveyor 6 to the conveyor belt 7. These determining means 10 determine the shape of at least one side of the belt strip. The shape as determined of the at least one side is compared in comparison means (not shown) with the shape of a reference side concerned. For this purpose, the comparison means are connected to the determining means 10 and preferably comprise a first memory for storing the shape as determined of the at least one side of the strip, a second memory for storing the shape of the at least one reference side concerned, calculating means for calculating the difference between the shape as determined of the at least one side and the shape of the reference side, and control means for controlling the adjusting means (not shown), depending on the calculated difference. These adjusting means adjust the shape of the at least one side to the reference side, depending on the calculated difference. In order to keep the drawing simple, only determining means 10 for belt material present on the upper conveying means 6, 7, 8 have been shown. It will be clear, however, that analogous determining means can be present at the lowest conveying means. The building drum 1 can have various diameters, depending on the diameter of the pneumatic tyre which is to be produced. The minimum diameter has been represented by a continuous line, the maximum diameter of the building drum 1 has been represented by interrupted lines. In order to allow for the manufacture of pneumatic tyres having greatly differing diameters, the frame 11 of the building drum 1 is constructed such that building drums may exchangably be mounted thereon. Figure 2 shows a schematic top view of a part of the belt strip feeding apparatus represented in figure 1. The roller conveyor 6 is built up by a number of bearing rollers 12, each of which is driven such that belt material 13 which is present on the roller conveyor 6 is conveyed to the conveyor belt 7. The belt material 13 is herein centered at the beginning of the roller conveyor 6 by guide rollers 14 on both sides of the belt material 13. When the belt material 13 has arrived in a position under adjustable cutting means 9, the belt material 13 is cut under an angle α, which lies for instance between 18° and 30°. When the belt material has been reinforced by steel cords running almost parallel to each other, said cords enclosing an acute angle with the imaginary centre line of the material, the belt material is preferably not fixed during cutting. As a result, the cutting means 9 can cut the belt material between the cords, without the steel cords becoming exposed. After cutting, the roller conveyor 6 conveys the cut belt material 13 further in the direction of the conveyor belt 7, as shown in figure 3. The roller conveyor 6 comprises two parts 6a and 6b which can be coupled by means of an electro-magnetic coupling (not shown). The bearing rollers of the part 6a extend, at the cutting means 9, from one edge of the roller conveyor upto a distance from or upto the line of cut determined by the cutting means, such as for instance roller 12'. Opposite bearing roller 12' of part 6a a bearing roller (not shown) of part 6b extends upto the other edge of the roller conveyor. During further conveyance the belt material is pressed against guide rollers 16 by a pressure roller (not shown) situated above. When the belt material 13 passes the transition 15 between roller conveyor 6 and conveyor belt 7, then, as will be described in more detail later, at least one side of the belt material is adjusted to a reference side. When the belt material 13 has covered a distance from the cutting means 9 which corresponds to the desired length of a belt strip, then the conveyance of the belt material is stopped and the cutting means 9 are activated to cut the belt material, thus forming a belt strip. This belt strip 17 is further conveyed by part 6b of the roller conveyor 6 in the manner as shown in figure 4. When the belt material reaches the conveyor belt 7, the adjusted shape of the side is fixed by fixing means which fix the belt material on the conveyor belt 7. These fixing means can be formed for all types of belt material, so including non-ferro belt material, by pressures belts placed above the conveyor belt 7 or vacuum means below the conveyor belt 7. When the belt material has been reinforced with steel cords, the fixing means are preferably formed by magnets 18, as shown in figure 5. Depending on the surface of the belt strip present on the conveyor belt 7, great forces are exercised on the conveyor belt when the belt strip is pulled against the conveyor belt 7 by the magnets 18. If these forces become too great, the conveyor belt 7 could start to slip in an unchecked manner, which would be harmful to the adjusted shape. In order to prevent the conveyor belt from slipping in an unchecked manner, the conveyor belt 7 should be driven without variations or with a constant (small) slip. A driving of the conveyor belt 7 without variations or with a constant (small) slip is for instance obtained by driving the conveyor belt 7 with three drivable drive rollers 19, 20 and 21. One of these drive rollers 21 is placed at the end of the conveyor belt 7 and two of these somewhere halfway the conveyor belt 7. These two drive rollers 19, 20 are positioned relative to each other in such a way that the conveyor belt 7 passes between them in an S-shape. Moreover, practice has shown that, depending among other things on the velocity of the conveyor belt relative to the permanent magnet 18, the conveyor belt 7 can execute a movement transverse to its direction of travel, which has a negative effect on the adjusted shape of the at least one side of the belt strip. By laterally confining the conveyor belt 7 by means for laterally restricting the freedom of movement of the conveyor belt 7, this negative effect is avoided. These means can be formed by raised edges between which the conveyor belt 7 is placed. The conveyor belt 7 preferably comprises an encoder 22 for measuring the movement of the conveyor belt 7. Although there are other means for measuring the movement or shift of the conveyor belt, which measurement could be used to measure the shape of a certain side of the belt strip, an encoder is preferred because it provides a real time measurement. The conveyor belt is controlled by a drive unit 23 with an (other) encoder coupled thereto. In the present case, the drive rollers 19, 20, 21 are connected to the roller conveyor via geared belts, so that the (other) encoder also controls the movement hereof. Although adjusting the shape of at least one side of a strip of flexible material, such as a belt strip, to a reference side concerned, may be carried out in the statical manner after determining the shape, as described in US patent specification 4,608,890, the invention will be described by means of a dynamic adjustment which takes place during the transition of the belt material from the roller conveyor to the conveyor belt. In such a dynamic adjustment, sections of the at least one side are successively adjusted to sections of the reference side concerned. The cycle time for conveying the belt material, cutting the belt strip, adjusting the belt strip to a reference strip and further conveying it to a building drum turns out to be sufficiently short for mass production when the dynamic adjustment is carried out by moving the belt material 13 relative to the conveyor belt 7 transverse to the direction of conveyance 30 during the transition 15 of the belt material from the roller conveyor 6 to the conveyor belt 7, as is schematically shown in figure 6. This relative transverse shift takes place by shifting the entire roller conveyor 6, on which the belt material 13 is situated, controlled by an electronic unit 24 transverse to its direction of conveyance 30. As a result, the belt material situated on the roller conveyor 6 moves relatively vis a vis the conveyor belt 7, with encoder 22 and raised edges 27 for confining the conveyor belt 7. The electronic unit 24 controls the lateral shift of the roller conveyor, depending on the calculated difference between the shape of the at least one side of the belt material and the reference side. The dynamic adjustment can possibly be stabilized by bringing the belt material 13 between two pressure rollers 25, 25', which pressure rollers 25, 25' are coupled to the roller conveyor 6. The rollers 25, 25' are cylindrical, and their axis is transverse to the direction of conveyance and they have preferably parallel circumferential grooves. Furthermore, a cylindrical roller 26 provided with parallel circumferential grooves is situated above the beginning of the conveyor belt 7 for pressing the belt material 13 against the conveyor belt 7. The roller 26 aids in fixing the adjusted shape of the at least one side, since making the permanent magnet 18 reach up to the beginning of the conveyor belt 7 (figure 7) would only be possible in a very complicated and expensive manner. In order to render a correct determination of the shape of the at least one side possible, the transition 15 should have a sufficient width. On the other hand, the transition 15 should not be too wide, because in that case no sufficiently correct adjustment would be possible. In acutal practice, it has been found that a width of about 7 mm for the transition 15 satisfies both requirements. The diameter of the rollers 25, 25' should therefore be such, that such a width can be realized. Alternatively, obtaining a transverse relative shift of the belt material is possible by shifting the conveyor belt 7 transverse to its direction of conveyance, or by clamping the belt material 13 between two pressure rollers 25, 25', and by exclusively shifting these pressure rollers 25, 25' transverse to the direction of conveyance. Determining the shape of the side of the belt material to be adjusted is preferably carried out during the transition 15 from roller conveyor 6 to conveyor belt 7 by linear CCD-cameras 31 and 31' placed above the transition, which cameras are incorporated into a common housing 28, as shown in figures 7 and 8. By incorporation into the common housing 28, the mutual position of the CCD-cameras 31, 31' is accurately fixed. A lamp 29 is placed under the transition 15, said lamp sending light to the CCD-cameras 31, 31'. The linear CCD-cameras 31, 31' can accurately detect the presence and the position of the belt material between lamp and cameras. The lamp 29 preferably is a HF-TL-lamp, of for instance 100 Hz, to avoid interference by ambient light. Other ways of determining the position, and thus the shape of a side, of the belt material can also be used in the invention. Determinations by IR detectors or by means of lasers or induction measuring equipment is possible, although they are often more expensive than the use of linear CCD-cameras. Hereafter, adjusting an actual belt strip to a reference strip will be described in more detail. It will be clear that not all steps need necessarily be carried out, but that, depending on the quality of the supplied belt material and the cutting process, one or more steps can be omitted. Figure 9 schematically shows an ideal shape of a belt strip, which can be used as reference belt strip. The belt strip 17' is elongated and has in general a length L of between 1400 and 3100 mm and a width b of between 80 and 300 mm. The belt strip 17' has two long circumferential sides and two short circumferential sides 35', 39'. The belt strip comprises a central rectangular part 32' having two long sides 37' and 38' and a centre line 41', a leading end 33' and a trailing end 34'. The triangular leading end 33', situated downstream, has an hypotenuse forming the short, leading circumferential side 35' and a short side 36' forming the one long circumferential side of the belt strip 17' together with the long side 37' of the central part 32'. The hypotenuse 35' and the short side 36' enclose an acute angle α, which in general lies between 18° and 30°. The acute angle α corresponds to the angle under which a great number of parallel running steel reinforcement cords 43 lie in the belt material. The triangular trailing end 34', situated upstream, has an hypotenuse forming the trailing, short circumferential side 39' of the belt strip 17' and a short side 40' forming the other long circumferential side of the belt strip 17' together with the other long side 38' of the central part 32'. Figure 10 schematically shows a belt strip 17 as it usually looks after cutting. The width of the central part 32 can vary in practice by 2 mm, the variation in width being far from symmetrical. Because the belt material is wound on supply reels, tensions are created in the material. Additionally, the difference in tension between steel reinforcement cords, which often consist of several intertwined wires, and the rubber material between the cords also creates tensions in the material. After cutting, these tensions relax, as a consequence of which the corner of the leading and trailing end bends randomly inwards, outwards or upwards. Consequently, the actual shape of the hypotenuse deviates from the path travelled by the knife of the cutting means. It is remarked that the long side 37 in the present case is relatively straight due to the one-sided centering by guide rollers 16 (see figure 3). It is, among other things, the object of the invention to adjust this actual shape as accurately as possible to this reference shape or to other references. Thus, it is for instance possible to adjust the shape of the trailing short end 39 to the shape of the leading short end 35 and not to a reference side such as 39'. Figure 11 schematically shows a top view of the transition 15 between roller conveyor 6 and conveyor belt 7 with imaginary centre line 53. The belt material 13 is conveyed such that the corner of the leading end 33 is situated exactly between the CCD-cameras and the HF-TL lamp (not shown). From this position, the belt material 13 is further conveyed to the conveyor belt 7, which conveyance is controlled by a second encoder. The position of the short side and/or the hypotenuse of the leading end 33 is each time determined after every pre-set distance by the linear CCD-cameras and the HF-TL lamp, the linear cameras having a direction of scanning which is transverse to the direction of conveyance. The encoder also controls the fact that the conveyor belt has covered the pre-set distance and that a determination should be executed. It has been found that when the pre-set distance corresponds to half the average distance between the steel reinforcement cords, the adjustment can be carried out best. This half the average distance is in general about 1½ mm. After the position of the short side and/or the hypotenuse has been determined, this position is compared to the position taken up by the reference side in this position and the difference between them is determined. This difference is corrected by shifting the roller conveyor 6 over a distance d which corresponds to that difference (see figure 12). This distance d is generally below 3 mm. The belt material 13 is further conveyed until it reaches the conveyor belt 7 where it is fixed. Although during this further conveyance the belt material can once again be shifted (by the next adjustment) somewhat laterally before the belt material reaches the conveyor belt, the deviation of the small front corner of the leading end which may possibly have been introduced hereby turns out to be almost negligible and to lie within the tolerances. The speed of the determination is such that the belt material can be conveyed continuously, the velocity of conveyance for adjusting the front part of the leading end (about the first 20-30 mm thereof) being reduced, since it is precisely at this point that the difference in distance d is greatest and that the roller conveyor should have sufficient time to cover this distance between two determinations of position. When the entire belt strip 17 has been conveyed to the conveyor belt 7, the shape of the belt strip has been determined across its entire length. The determining grid is then as shown in figure 13. The grid lines 44 are spaced as intervals of about 1½ mm. The positions of the belt strip edges, determined by the CCD-cameras, are transmitted to a first memory of comparison means. These comparison means comprise a second memory, containing the parameters necessary to determine the reference sides. These parameters describe among other things: the position of the imaginary centre line 43 of the conveyor belt 7 (or another fixing element such as a building drum), the width b r of the reference belt strip (or the average width of one or more belt strips which have been adjusted prior to the current belt strip), the length of the reference belt strip, the length of the central part, the length of the short side of the leading and trailing end, the size of the acute angle α for determining the position of each point of the hypotenuse at a certain distance from the point of the leading end, possible corrections to the above-mentioned parameters, possible other apparatus parameters. The comparison means also comprise calculating means for calculating the difference between the position as determined and the reference position, and control means for controlling the electronic unit which controls the lateral shift of the roller conveyor. The leading end 33 can be adjusted to the reference leading end in two ways. On the one hand, the short side 36 can be adjusted to the reference short side 36' (figure 9). On the other hand, the hypotenuse 35 can be adjusted to the reference hypotenuse 35' (figure 9). For the first adjustment, the difference Δ ℓ between the long side of the current belt strip 17 and the reference long side is calculated. The roller conveyor is shifted over this distance Δ ℓ , so that the long side of the current belt strip is placed at ½ b r from the imaginary centre line 53 of the conveyor belt. This calculation of Δ ℓ and the corresponding shift is successively carried out from grid line 1, 2, ... to the last grid line scanning the leading end. During each scan along a grid line, preferably the width of the leading end is determined and stored. The last grid line scanning the leading end can be determined by the parameter for the length of the short side of the leading end (ℓ LE ) or by observing the measured variation in width of the leading end. A slight variation in width indicates that the grid lines have reached the central part of the belt strip. For the latter adjustment, the difference Δ h between the hypotenuse 35 of the current belt strip 17 and the reference hypotenuse 35' is calculated. The roller conveyor is shifted, depending on this difference, over a distance, such that the position concerned of the current hypotenuse 35 (for instance in the point on grid line 5) coincides with the position relative to the reference centre line 41' indicated by the parameters. In this way, the shape of the current leading edge is determined, thus providing a possibility to check the quality of the cutting process and the belt material, and the shape of one side of the leading end is adjusted with an accuracy in the order of the variation in width of the material. Of course, adjustment of the one side does not automatically mean that the other side has also been accurately adjusted. In practice it has been found, however, that when the belt material meets the usual specifications stated by the manufacturers of tires, the other side also falls within the tolerances. When the central part 32 of the belt material is situated between the CCD-cameras and the HF-TL lamp, the mutual position of the long sides 37 and 38 of the central part 32 is determined, and the width of the central part 32. Per grid line, the middle m c of the central part 32 is determined and the deviation Δ c hereof relative to the reference centre line 41'. The roller conveyor is shifted such, depending on the determined deviation Δ c , that the middle of the central part coincides with the reference centre line. Owing to this, the central part is placed symmetrically around the reference centre line. This provides a good uniformity in the pneumatic tyre which ultimately is to be manufactured. Since the width of the central part can vary by about 2mm, the adjusted long sides 37 and 38 of the current belt strip are not identical to the reference long sides 37' and 38'. However, this deviation is relative to the reference centre line is halved so that now, too, the central part once again meets the set tolerance limits. Moreover, it is possible to use for reference width b r the average width of the central part of the preceding belt strip, which average width is stored as parameter in the comparison means. As a result of this, it is achieved that the leading and the trailing end, when they are wound around the building drum, fit together accurately, even when the belt material does not, to a certain extent, meet the specifications. The adjustment of the trailing end 34 can also take place in two ways. On the one hand, the short side 40 can be adjusted to the reference short side 40', while on the other hand, the hypotenuse 39 can be adjusted to the reference hypotenuse 39'. These adjustments take place analogously to the adjustments described for the leading end. It has been found, however, that when switching from the adjustment to the reference centre line 41' to the adjustment of the short side 40 to the reference short side 40', a discontinuity can occur in the belt strip which leads to a deviant shape. In order to prevent this, it is preferred that a rear part 42 of the central part 32 is not adjusted to the reference centre line 41', but that the part of the long side 38 belonging to this rear part 42 is adjusted to the reference side 38'. Thus, the final adjusted belt strip will become more regular. The length of this rear part 42 can differ per belt material, but has been found to usually lie between 10 and 30 mm. The comparison means also serve to contain a value for the width of this rear part 42' (figure 9), to indicate the switch between the two different adjustments. When switching from an adjustment to the reference line 41' to an adjustment of the hypotenuse 39 to the reference hypotenuse 39', then it is to be preferred that of the first part 52 of the trailing end 34, for instance the first 10 mm, the short side 40 is adjusted to the reference short side 40' to avoid a similar discontinuity. When the short side of the leading end has been adjusted to the reference short side, it is possible to adjust the hypotenuse 39 of the trailing end 34 to the hypotenuse of the leading end. This adjustment is possible because each time the width b LE of the leading end is determined. Although the measured width of the leading end differs from the width of the leading end after adjustment, this difference is so small in actual practice, often in the order of the variation in the width of material, that this has no effect on this adjustment. The hypotenuse 44 of the leading end after adjustment has been shown in figure 14. During determination of the shape of the trailing end 34, the width B TE is measured each time. In the comparison means the difference is now calculated between b r -b LE -B TE =Δ b . The roller conveyor is laterally shifted over this difference Δ b , so that ultimately the hypotenuse of the trailing end and that of the leading end have a complementary shape. The adjustments described above can be carried out in this way because the shift of the conveyor belt on the roller conveyor is continuously monitored, for instance by the encoder. The comparison means therefore know at what moment which part of the reference strip should be taken for comparison with the current belt strip. After the entire adjusted belt strip has come to lie on the conveyor belt, the roller conveyor is preferably brought to its starting position. With the method and the apparatus according to the invention, a belt strip can be adjusted to a reference in such a way that further working of or with the adjusted belt strip can take place accurately and reproducibly. When the adjusted belt strip is mounted about a building drum, the centering thereof has been found to fall within the tolerance limits because the central part is positioned symmetrically relative to a reference centre line, which of course in that case is aligned relative to the building drum, and the leading and trailing, short end fit together within the tolerance limits. It will be clear to a person skilled in the art that the reference sides with which the sides of the current belt strip are compared, can be different from those as shown in the figures. Applying a step or a curve is possible in order to make a certain correction for a current production environment. Furthermore, the adjustment can also be carried out without the use of a conveyor belt, for instance by carrying out the adjustment between the transition from the roller conveyor to the building drum. When a conveyor belt is used for further conveying the adjusted belt strip, then the length of the belt strip is preferably measured on the conveyor belt. Especially when the belt strip has been reinforced with steel cords, impenetrable to the knife of the cutting means, the length of the belt strip varies by approximately the thickness of the cord. The measured actual length can be adjusted to the circumference of the building drum, by varying the velocity of the mounting conveyor relative to the velocity of rotation of the building drum. If the velocity of the mounting conveyor is smaller, then the belt strip is stretched during mounting on the building drum. If the speed is higher, then the belt strip is clenched. Furthermore, the invention is not only applicable in a belt strip feeding apparatus, but also in a cutting apparatus where strips of rubber material containing steel cords 61, which run in longitudinal direction, are cut into belt strips 62 (figure 15). This invention is also especially applicable when attaching these strips 62 having pointed corners.

Claims: Method for feeding a belt strip (17) to a rotating building drum (1), said method comprising the steps of: a) unwinding belt material (13) having opposite longitudinal sides from a supply reel (2, 3), b) conveying the belt material (13) in a direction of conveyance (30) at a velocity of conveyance from the supply reel (2, 3) to a fixing element by conveying means, said longitudinal sides of the belt material (13) being substantially parallel to the direction of conveyance (30), said conveying means being spaced from the fixing element forming a transition (15) between the conveying means and the fixing elements, said conveying means comprising a first conveyor (6, 6'), c) cutting the belt material (13) into a belt strip (17) by cutting means (9, 9') placed above the conveying means, said belt strip (17) being elongated and having two long circumferential sides (37, 38) and two short circumferential sides (35, 39), said belt strip (17) comprising: a central rectangular part (32) having two long sides and an imaginary centre line (41), the direction of conveyance (30) of the first conveyor (6, 6') being parallel to the imaginary centre line (41), a triangular leading end (33), situated downstream, the one short, leading circumferential side (35) of the strip (17) being formed by the hypotenuse of the leading end (33) and a short side (36) of the leading end (33) lying in the extension of one (37) of the long sides (37, 38) of the central part (32), the hypotenuse (35) and the short side (36) of the leading end (32) enclose an acute angle and the one long side (37) of the central part (32) and the short side (36) of the leading end (33) forming the one long circumferential side of the strip (17), a triangular trailing end (34), situated upstream, the other short, trailing circumferential side (39) of the strip (17) being formed by the hypotenuse of the trailing end (34) and a short side (40) of the trailing end (34) lying in the extension of the other side (38) of the central part (32), the hypotenuse (39) and the short side (40) of the trailing end (34) enclosing an acute angle and the other long side (38) of the central part (32) and the short side (40) of the trailing end (34) forming the other long circumferential side of the strip (17), d) conveying the belt strip (17) over the transition (15) whereby successively adjacent sections of the belt strip (17) are conveyed over the transition (15), e) determining the shape of at least one side of the belt strip (17) after the step of cutting the belt material (13) during conveyance of the belt strip (17) over the transition (15) between the conveying means and the fixing element, said step of determining being effected by determining the shape of the sections of the at least one side, storing said shape in a first memory, f) comparing the shape of the sections of the at least one side of the belt strip (17) stored in the first memory with a shape of corresponding sections of a reference side which has been stored in a second memory, g) adjusting the shape of the sections of the at least one side of the belt strip (17) to the shape of the corresponding sections of the reference side during conveyance of the belt strip sections over the transition (15), by moving the sections of the belt strip (17) relative to the fixing element transverse to the direction of conveyance (30), and h) fixing the thus adjusted shape of the sections of the at least one side of the belt strip (17) on the fixing element (7) by fixing means (18). Method according to claim 1, wherein the fixing element is formed by a conveyor belt (7, 7'). Method according to claim 1, wherein the fixing element is formed by the building drum (1). Method according to claim 1, 2 or 3, wherein the at least one side is formed by the short side (36) of the leading end (33). Method according to claim 1, 2 or 3, wherein the at least one side is formed by the hypotenuse (35) of the leading end (33). Method according to claim 1, 2 or 3, wherein the at least one side is formed by the hypotenuse (39) of the trailing end (34). Method according to claim 1, 2 or 3, wherein the at least one side is formed by the short side (40) of the trailing end (34). Method according to any one of the preceding claims, wherein the method further comprises the steps of determining the shape of the centre line (41) of the central part (32), comparing the shape of the centre line (41) of the central part (32) with a shape of a reference centre line (41') and adjusting the shape of the centre line (41) of the central part (32) to the shape of the reference centre line (41'). Method according to any one of the preceding claims, wherein the method further comprises the step of measuring the width of each section. Method according to claim 9, wherein the width is measured every 1½ mm. Method according to any one of the preceding claims, wherein the determination of the shape of the at least one side is done by means of two linear CCD-cameras (31, 31'). Belt strip feeding apparatus for feeding a belt strip (17) to a rotating building drum (1), which feeding apparatus comprises: a supply reel (2, 3) for containing belt material (13), means (4, 5) for unwinding belt material (13) from the supply reel (2, 3), conveying means for conveying the unwound belt material (13) to the building drum (1), successively comprising a roller conveyor (6, 6'), a conveyor belt (7, 7') and a mounting conveyor (8, 8') for mounting the belt strip (17) onto the building drum (1), said roller conveyor (6, 6') being spaced from the conveyor belt (7, 7') forming a transition (15) between the roller conveyor (6, 6') and the conveyor belt (7, 7'), said roller conveyor (6, 6') being movable in a direction transverse to its direction of conveyance (30), cutting means (9, 9') placed above the roller conveyor (6, 6') for cutting the belt material (13) into a belt strip (17), such that the belt strip (17) is elongated and has two long circumferential sides and two short circumferential sides (35, 39) and that the strip comprises: a central rectangular part (32) having two long sides (37, 38) and an imaginary centre line (41), the direction of conveyance (30) of the roller conveyor (6, 6') being parallel to the imaginary centre line (41), a triangular leading end (33), situated downstream, the one short, leading circumferential side (35) of the strip (17) being formed by the hypotenuse of the leading end (33) and a short side (36) of the leading end (33) lying in the extension of one (37) of the long sides (37, 38) of the central part (32), the hypotenuse (35) and the short side (36) of the leading end (33) enclosing an acute angle and the one long side (37) of the central part (32) and the short side (36) of the leading end (33) forming the one long circumferential side of the strip (17), a triangular trailing end (34), situated upstream, the other short, trailing circumferential side (39) of the strip (17) being formed by the hypotenuse of the trailing end (34) and a short side (40) of the trailing end (34) lying in the extension of the other side (38) of the central part (32), the hypotenuse (39) and the short side (40) of the trailing end (34) enclosing an acute angle and the other long side (38) of the central part (32) and the short side (40) of the trailing end (34) forming the other long circumferential side of the strip (17), determining means (10) for determining the shape of at least one side of the strip (17), said determining means (10) being positioned at the transition (15) from the roller conveyor (6) to the conveyor belt (7), comparison means for comparing the shape as determined of the at least one side to the shape of a reference side, adjustment means controlled by control means (24) for adjusting the shape as determined of the at least one side to the shape of the reference side, depending on the outcome of the comparison, by moving the roller conveyor (6) in a direction transverse to its direction of conveyance (30), and fixing means provided on the conveyor belt (7) for fixing the adjusted belt strip (17) on the conveyor belt (7), wherein the comparison means comprise a first memory for storing the shape as determined of the at least one side of the strip (17), a second memory for storing the shape of the at least one reference side concerned, calculating means for calculating the difference between the shape as determined of the at least one side and the shape of the reference side, and an electronic unit (24) for controlling the adjusting means, depending on the calculated difference. Belt strip feeding apparatus according to claim 12, wherein a pair of rollers (25, 25') is attached to the end of the roller conveyor (6), which pair of rollers (25, 25') is placed between the roller conveyor (6) and the conveyor belt (7), such that a gap is formed between the pair of rollers (25, 25') and the conveyor belt (7), between which pair of rollers (25, 25') the belt strip (17) can be clamped. Belt strip feeding apparatus according to claim 12, in which the belt material contains magnet-sensitive material, wherein the fixing means provided on the conveyor belt (7) contain magnets (18) for fixing the belt strip (17). Belt strip feeding apparatus according to claim 14, wherein the conveyor belt (7) is driven with as small a constant slip as possible. Belt strip feeding apparatus according to claim 14 or 15, comprising raised edges (27) for restricting the freedom of movement of the conveyor belt (7) in lateral direction. Belt strip feeding apparatus according to any one of the claims 12 to 16, wherein the conveyor belt (7) comprises an encoder (22) for measuring and a drive unit (24) for controlling the movement of the conveyor belt (7). Belt strip feeding apparatus according to claim 12, wherein the apparatus comprises guide rollers (14) for feeding the belt material (13) to the cutting means (9, 9') in a centered manner. Belt strip feeding apparatus according to claim 12, wherein the determining means are formed by two linear CCD-cameras (31, 31') and a high frequency lamp (29), between which cameras (31, 31') and lamp (29) the belt strip (17) is conveyed.

Inventors: REGTERSCHOT MARTINUS, TER HORST ANTHONIUS ARNOLDUS C, REGTERSCHOT, MARTINUS, TER HORST, ANTHONIUS ARNOLDUS CAROLUS
Applicants: VMI EPE HOLLAND, VMI EPE HOLLAND B.V.
Application year: 1994
Main classification: B29D30
IPC codes: B65H9, B29D30